Current light engines sometimes include reflective surfaces that collect and focus light onto end surfaces of large core optic or fiber optic light pipes. Some current systems also include means for dissipating heat and protecting light pipes from heat-related damage that might otherwise result from the intense heat typically associated with high-intensity illuminators and convergent light beams.
One method of focusing at least a portion of light from an illuminator onto a light pipe end surface is to incorporate a hollow half-ellipsoid reflector shell into a light engine. According to this method, an illuminator is disposed at a first focal point of the reflector shell and a light pipe end surface is disposed at a second focal point of the reflector shell.
For example, U.S. Pat. No. 5,099,399 to Miller et al. (the Miller patent) discloses a light engine that uses a half-ellipsoid reflector dish to focus light energy from an illuminator onto the end of a large core optic light pipe. The light engine includes a lamp casing and a tubular receptacle for receiving one end of the light pipe. The illuminator is included in a lamp disposed inside the lamp casing. A glass thermal barrier is disposed in the tubular receptacle between the lamp and the large core optic light pipe. The illuminator is disposed at a first focal point of the half-ellipsoid reflector dish. An inner surface of the thermal barrier is disposed at a second focal point of the reflector dish. The reflector dish focuses light emitted from the illuminator onto the thermal barrier inner surface.
The Miller patent also discloses a radiation heat dissipation system comprising fins and a convective heat dissipation system comprising an electric fan and a series of air channels passing through the tubular receptacle and the lamp casing. The inclusion of these various heat dissipation systems gives the Miller light engine a complex structure that is difficult to fabricate and assemble and that includes moving parts that require additional electrical energy to operate and are inherently maintenance-prone, e.g., the electric fan motor. In addition, the Miller patent discloses no provision for recovering light energy that is lost when the light energy radiates from the light source and reflects from or is absorbed by an inner surface of the lamp casing rather than reflecting off the half-ellipsoid reflector.
U.S. Pat. No. 4,883,333 to Yanez (the Yanez patent) discloses a full-ellipsoid reflector. An illuminator is disposed at a first focal point within the ellipsoid reflector. The reflector focuses light from the illuminator onto a second focal point within the ellipsoid reflector. The Yanez reflector comprises a reflective coating on a solid ellipsoid formed from optical material. The Yanez light source is embedded within the optical material.
The Yanez reflector focuses light on a lens integrally formed with a cone channel condenser. The Yanez patent discloses no provision for dissipating heat generated by the light source or for replacing the light source when it burns out. The Yanez patent also discloses no provision for protecting the light pipes from heat energy that the illuminator might generate.
U.S. Pat. No. 5,416,669 to Kato et al. (the Kato patent) discloses a light engine having two intersecting, outwardly facing half-ellipsoidal reflector dishes. A single illuminator is disposed at a point that is the first focal point of both reflector dishes. Two light pipes extend inward, from outside the light engine, through a pair of tubular receptacles to the second focal point of each reflector dish.
Glass thermal barriers are disposed in the tubular receptacles between the lamp and the large core optic light pipes. Because the reflectors are only half-ellipsoidal, much of the light from the illuminator does not impinge upon the reflectors. Therefore, the Kato light engine includes a second set of annular mirrored surfaces that re-direct light that does not impinge upon the half-ellipsoid reflector dishes. The resulting structure includes complex contours that are difficult to machine.
It is desirable for light engines that condense light onto end surfaces of large core optic light pipes to include reflective surfaces and heat dissipation systems that are both effective and relatively simple and inexpensive to manufacture and operate.